Adenosine receptors in rat testes: Labeling with ³Hcyclohexyladenosine

We have labeled adenosine receptors in rat tissues with ³HN⁶cyclohexyladenosine (³HCHA) and evaluated the organ distribution and drug specificity of these binding sites throughout the body. Detectable receptor concentrations are restricted to the brain and testes. Brain displays receptor levels of 9 pmoles/g wet weight of tissue while the testes display 2 pmoles/g, with all other tissues examined showing less than detectable specific binding of ³HCHA. The receptors in these two tissues appear to possess identical pharmacologic profiles with an A₁ specificity for both. No change in the total number of ³HCHA binding sites is seen in testes of rats which had been hypophysectomized 14 days prior to sacrifice. This may exclude the Leydig cells as a source of adenosine receptors in the rat testes.